(a) Field of the Invention
The present invention relates to a variable tappet.
(b) Description of the Related Art
In typical light load driving, the driver uses only around 30% of an engine's maximum power. In these conditions, the throttle valve is nearly closed, and the engine needs to work to draw in air. This causes cylinder pressure to be very low leading to low fuel efficiency.
Cylinder deactivation is thus used at light load so that the throttle valve can be opened further to provide the same power output. This increases pressure in each cylinder. Cylinder deactivation is achieved by keeping the intake or exhaust valves closed for a particular cylinder.
A typical cylinder deactivation apparatus includes a three-part variable tappet, a lock pin, and a double cam. The three parts of the tappet can be separated from one another and cooperate with the double cam to deactivate a cylinder.
The double cam and variable tappet are costly to manufacture and complicated to assemble.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.